Field of the Invention
The present invention relates to a fuel tank system, and more particularly to pressure detection structure in a closed type fuel tank.
Description of the Related Art
In a conventional fuel tank system, there is a technique for preventing release of a fuel evaporative emission formed by evaporation in a fuel tank into the atmosphere, in which a sealing valve (hereinafter referred to as a tank blocking valve), which is controlled so as to close the fuel tank, is provided in a path allowing the fuel tank to communicate with a canister. The tank blocking valve is opened at the time of filling so that the fuel evaporative emission is allowed to flow to the canister, thereby allowing the canister to absorb the fuel evaporative emission.
In such a fuel tank system, if the fuel tank is closed by the tank blocking valve, fuel in the fuel tank evaporates with a rise in outside air temperature, so that pressure in the fuel tank, or fuel tank internal pressure, may become high due to a fuel evaporative emission.
Japanese Patent Laid-Open No. 2013-92135, for example, describes a fuel evaporative emission preventing device, in which a pressure sensor is provided in a fuel tank to monitor fuel tank internal pressure, and if a fuel tank internal pressure becomes high while an engine is operating, a tank blocking valve is opened to allow a fuel evaporative emission in the fuel tank to flow into an air intake passage of the engine so that the fuel tank internal pressure is reduced.
In the fuel evaporative emission preventing device, a pressure sensor for detecting the fuel tank internal pressure is provided in a fuel tank to control an operation of a tank blocking valve on the basis of a detection value obtained by the pressure sensor.
Unfortunately, if abnormality occurs in the pressure sensor, there is a possibility that pressure in a fuel tank cannot be accurately detected so that a lid of a filling opening cannot be properly opened.